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충격파 -경계층 간섭 유동에서 k-ω 와 k-e 난류 모델의 수치적 비교 연구
최재형,염효원,성홍계 한국항공우주학회 2011 한국항공우주학회 학술발표회 논문집 Vol.2011 No.11
충격파 - 경계층 간섭유동에 적합한 난류 모델을 비교하는 수치해석을 수행했다. k-ω 와 k-ε 난류 모델에 압축성 효과를 고려하기 위해 Sarkar 와 Wilcox 모델을 조합하였다. 경계층과 자유 유동의 정확한 조건을 추정하기 위하여 시험물을 포함한 풍동장치 전 영역을 모델링하여 수치해석을 수행하였다. k-ω와 k-ε 모델의 결과는 두드러진 계산 결과의 차이가 발생하였는데, k-ε 모델에서는 압축성 효과가 많은 영향을 미치고 있으나 k-ω 모델에서는 압축성 효과에 의한 차이가 크게 발생하지 않았다. 본 연구에 소요되는 계산시간의 효율성을 위하여 계산영역을 다중 블록으로 구성하였으며, MPI(Message Passing Interface) 병렬 계산 기법을 적용하였다. To validation of turbulence models suitable for the shock - boundary layer interaction, numerical analysis was performed. The turbulent effects are modeled utilizing two-equation turbulence models, the low Reynolds k-ε and the k-ω SST models with compressibility corrections proposed by the Sarkar and Wilcox. The numerical domain of concern includes the wind tunnel experimental equipment and test section as well. There is a noticeable distinction between results of k-ω and k-ε models. For compressibility effect, the k-ω model has provided similar results, however the k-ε model has brought relatively different results. The code is paralleled with multi-block feature using MPI(Massage Passing Interface) library to speed up the calculation.
$K-{\varepsilon}-{\tau}$ 난류모델을 이용한 축대칭 엔진 실린더내 유동장의 수치해석
최재성 한국마린엔지니어링학회 1999 한국마린엔지니어링학회지 Vol.23 No.5
Current turbulence models including modified $K-{\varepsilon}-{\tau}$ turbulence model do not predict compression effect on turbulence accurately in an internal combustion engine. The $K-{\varepsilon}-{\tau}$ turbulence model was suggested to improve the predictability of compression effect by We et al. In this paper a numeri-cal study was performed to clarify the applicability of the $K-{\varepsilon}-{\tau}$ turbulenc model to the calculation of the in-cylinder flow of an axisymmetric engine. THe results using $K-{\varepsilon}-{\tau}$ turbulence model are compared to those from the modified $K-{\varepsilon}-{\tau}$ turbulence model and experimental data. The mean veloc-ity and rms velocity profiles using $K-{\varepsilon}-{\tau}$ turbulence model showed a better agreement with an experimental data than those of modifid $K-{\varepsilon}-e$ turbulence model.
김광용,김정엽,정덕수,Kim, Gwang-Yong,Kim, Jeong-Yeop,Jeong, Deok-Su 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.4
Computational and experimental investigations on the three-dimensional flowfield through an automotive cooling fan are carried out in this work. Steady, incompressible, three-dimensional, turbulent flow through a rotating axial-flow fan is analyzed with Reynolds averaged Navier-Stokes equations and standard k-.epsilon. turbulence model. The governing equations are discretized with finite-volume approximations in non-orthogonal curvilinear coordinates. Computational static pressures on the casing wall agree well with the experimental data which are measured in this work. And, they are sensitive to the change of tip clearance. The flowfield is not significantly affected by the thickness of the blade. The k-.omega. model gives the static pressure rise on the casing wall which is similar to that with the k-.epsilon. model.
발열체와 격막이 있고 일부가 열린 복합공간내의 자연대류-복사열전달에 관한 수치적 연구
김태국,민동호,한규익,손봉세,서석호,Kim, Tae-Guk,Min, Dong-Ho,Han, Gyu-Ik,Son, Bong-Se,Seo, Seok-Ho 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.2
A numerical simulation on the combined natural convection and radiation is carried out in a partially open rectangular enclosure with a heater by using the finite volume and the S-8 discrete ordinate methods. The fluid inside the enclosure is considered as an absorbing, emitting and anisotropic scattering media. The heater causes a natural circulation of the fluid (10$^{5}$ <Ra<10$^{9}$ ) which results in significant in-flow of the ambient cold fluid through the partially open wall. Comparing the results of pure convection with those of the combined convection- radiation, the combined heat transfer results with small Planck numbers (P$_{l}$ <1.0) show much stronger circulation than those of the pure convection, and the fluid circulation is more evident for larger Rayleigh numbers. When one of three radiative properties - the medium absorption coefficient, the wall reflectivity, and the scattering albedo - increases, the fluid circulation and the heat transfer in the enclosure are reduced. The location of the heater and the open ratio of the right wall are also shown to affect the fluid circulation and heat transfer significantly. However, the anisotropy of the scattering phase function is shown to be unimportant for the fluid circulation and heat transfer within the enclosure considered in this study.
김성훈(S. H. Kim),손혜민(H. M. Son),이재천(J. C. Lee) 유공압건설기계학회 2011 드라이브·컨트롤 Vol.8 No.2
Analysis of two-dimensional flow in an involute gear pump has been done by using FLUENT. Analysis extended to the turbulent flow includes the mass flow rate with functions of pressure difference between inlet and outlet, rotational velocities of involute gear, and clearances between tip of gear and housing. In general mass flow rate decreases with decreasing rotational velocity, and with increasing clearance and pressure difference. The flow rate efficiency of gear pump, which is defined with the theoretical flow rate, has been presented in terms of the above parameters.